A Systematic Review of Mathematical Models for Soil-Transmitted Helminthiasis Control Strategies

BackgroundSoil-transmitted helminthiasis (STH) is a parasitic disease that affects over 1.5 billion people worldwide. The use of mathematical models to inform time-bound projections and support WHO targets is growing. Never-theless, there is a lack of comprehensive synthesis regarding the extent to which mathematical frameworks for STH control account for the timeframe and effectiveness of interventions required to meet WHO programmatic goals. ObjectiveThe present study aims to bridge this gap by classifying existing mathematical models based on their structural design and population features, assessing the effectiveness and impact of interventions in achieving WHO targets, and examining the timelines specified in these models for attaining WHO morbidity control and elimination goals. MethodsAn extensive search was conducted in the Web of Science, Scopus, and Embase databases to retrieve articles published in English between January 2015 and December 2024. The search query captured terms related to mathematical models, disease, and interventions. Articles on mathematical models of STH transmission dynamics that evaluated at least one control strategy were included. Extracted data included the type of model, intervention, study characteristics, population structure model, WHO policy alignment, and predictive outcomes. A narrative synthesis was conducted, and results were summarized thematically. The quality of the published articles was assessed using the Assessment Modeling Studies Tool. The protocol for this review is registered at PROSPERO (CRD420251090375). Principal findingsA total of 43 studies met the inclusion criteria. Stochastic models (47%) slightly outnumbered deterministic models (44%) and hybrid models (9%). Regarding model classification by population stratification, agestructured models (56%) were more prevalent compared to flat (28%) and spatial models (16%). Community- and school-based deworming were the most frequently modeled and compared interventions (42%), with community-based deworming (CBD) shown to interrupt STH transmission even in high-prevalence settings, outperforming child-targeted treatment strategies. Combination therapy was underexplored, representing only 7% of the studies. Sixty percent of the modeling studies aligned with the 2011-2020 morbidity control goals, while 40% aligned with the 2021-2030 transmission interruption objectives. Only 35% of the studies reported time-bound predictions, with significant variation in the duration required for a modeled intervention to reach WHO goals. The projected duration for attaining WHO targets ranged from 2 to 35 years under different intervention scenarios. Conclusions/significanceThe findings highlight the dominance of age-structured and stochastic models. Additionally, models demonstrate that community-wide treatment consistently outperforms child-targeted treatment strategies across most settings. However, there is insufficient time-bound modeling, underscoring the need for future research to explicitly include timelines for reaching WHO targets. Author summarySoil-transmitted helminthiases are parasitic worm infections acquired through contact with contaminated soil, primarily in low-resource settings. The World Health Organization (WHO) has established guidelines aimed at reducing the disease burden through either morbidity control or interruption of transmission. Mathematical models are essential tools for designing and evaluating STH control strategies in relation to meeting WHO-set targets. Many existing models report on reductions in prevalence or infection intensity. However, despite alignment with WHO goals, the time horizon required for modeled interventions to achieve the recommended targets has not been systematically synthesized. Therefore, this review synthesizes existing models by examining their structural design and population representation, how they predict the outcomes of interventions, and the timelines projected to achieve WHO goals. In this study, we synthesized 43 modeling studies and found that stochastic models (47%) were slightly more common than deterministic (44%) and hybrid (9%) approaches. Age-structured models (56%) were more widely used than spatial (16%) and non-structured (28%) frameworks. Comparisons between school-based deworming (SBD) and community-based deworming (CBD) (42%) were among the most frequently modeled interventions. Although all 43 studies aligned with WHO targets, only a minority (35%) explicitly reported the time required for modeled interventions to achieve morbidity control or elimination goals. Our findings highlight a critical gap: the lack of time-bound predictions in STH modeling. Addressing this gap in future research could improve strategic planning and policy decisions aimed at eliminating these infections.